New Wah Pots at AES, Different Values!

[zombiwoof]

Just thought I'd alert you guys to some new cheap way pots at AES (Tubesandmore.com).  They have the regular 100k, it doesn't say the taper, so it may be the standard ICAR, and three other linear values, 125k, 150k, and 200k in linear.  Might be a good option for some of you  that need a different value than the standard 100k.  And they are cheap, only $8.95 each!  Anybody try these yet?

I also wanted to tell you I noticed that Small Bear now has the wah pot gears in two types, one is the D-shaft style, and another fits a regular solid shaft pot, so you can use it on any regular pot you have.  Pretty cool.

Don't know if anyone has mentioned these before, my apologies if they have.

Al

[zombiwoof]

I forgot to tell you, to get to those wah pots at AES, click on "potentiometers", then on the link for "Dunlop/Wah".  I'd post a link, but you can't link directly to the page at AES.

Al

[Scruffie]

Aha, but you can, Right click, copy link location for future reference. 

http://www.tubesandmore.com/scripts/foxweb.dll/catalog@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?PAGE=SUBCAT&SEARCH_TREE01=08_POTENT&SEARCH_TREE02=10_DUNLOP

[Processaurus]

Thanks for the tip, I ordered a couple of the 125K linears to try in some crybaby chassi, as expression pedals.  I'll let you know how it goes.

[zombiwoof]

Definitely let us know what you think of them.  Maybe you can figure out who makes them, if there are any codes on the can.

Al

[RedHouse]

Definitely let us know what you think of them.  Maybe you can figure out who makes them, if there are any codes on the can.

Al

Us?

[Paul Marossy]

Huh, interesting. I wonder what affect these different value pots would have in the sound. It would be cool if someone had the time and money to try them all and let us know the outcome!  

[aziltz]

i had someone ask about tremolo in a wah case.  The EA uses 100k Linear I believe, and I didn't know how I'd be able to do it.  maybe now.

[Dai H.]

is it just my imagination or can some "100k" linear pots which are actually a bit higher work better in the vox/crybaby circuit? Old NOS pots IME (say, from the 60s, 70s) can have poorer tolerances tha modern ones, so perhaps on average the pots in old vox/crybaby wahs were further off from 100k, and (something like) 125k more closely replicates the old pots in reality(versus the stated value) and that is what is heard on recordings using the old wahs. 

[Paul Marossy]

is it just my imagination or can some "100k" linear pots which are actually a bit higher work better in the vox/crybaby circuit? Old NOS pots IME (say, from the 60s, 70s) can have poorer tolerances tha modern ones, so perhaps on average the pots in old vox/crybaby wahs were further off from 100k, and (something like) 125k more closely replicates the old pots in reality(versus the stated value) and that is what is heard on recordings using the old wahs. 

I measured the original scratchy pot in my old Vox wah from the early 70s. IIRC, it measured about 180K.

[zombiwoof]

Well, the "Blacktop" ICAR taper pot that is around is supposed to be a copy of the original RMC ICAR clone (it's a clone of a clone!), and it is 200k.  Geoffrey said that his was a copy of an old ICAR he had, so maybe those original ICAR's were not 100k.  I have one of those 200k ICAR copies in my Vox 847, and it works fine.  I have a feeling that it must not make a big difference, I think the taper is more important.

Al

[Paul Marossy]

Well, the "Blacktop" ICAR taper pot that is around is supposed to be a copy of the original RMC ICAR clone (it's a clone of a clone!), and it is 200k.  Geoffrey said that his was a copy of an old ICAR he had, so maybe those original ICAR's were not 100k.  I have one of those 200k ICAR copies in my Vox 847, and it works fine.  I have a feeling that it must not make a big difference, I think the taper is more important.

Al

Yeah, I think the consensus is that the taper matters more than if it's 100K vs. 200K.

I don't really care for my Vox wah a whole lot, it just sounds too harsh. I replaced the original pot with a 200K repro pot and it just doesn't really excite me at all.

[zombiwoof]

Well, the "Blacktop" ICAR taper pot that is around is supposed to be a copy of the original RMC ICAR clone (it's a clone of a clone!), and it is 200k.  Geoffrey said that his was a copy of an old ICAR he had, so maybe those original ICAR's were not 100k.  I have one of those 200k ICAR copies in my Vox 847, and it works fine.  I have a feeling that it must not make a big difference, I think the taper is more important.

Al

Yeah, I think the consensus is that the taper matters more than if it's 100K vs. 200K.

I don't really care for my Vox wah a whole lot, it just sounds too harsh. I replaced the original pot with a 200K repro pot and it just doesn't really excite me at all.

A stock Vox 847 needs a few resistor and transistor changes to make it sound more vintage.  In particular, the high gain trannies in there need to be changed out for some in the 300-350 hfe range, and the resistors that they changed from the vintage schematic need to be put back to original spec.  Not too difficult, and of course the true bypass mod and maybe an inductor change are also good.

Al

[Paul Marossy]

I guess I should have mentioned that my Vox wah is an early 70s model with a red Fasel inductor. It's supposed to be one of those mythical larger than life wahs, and I pretty much like it the least of all the wah pedals I have. About the only thing I was able to improve on it was making it not suck tone when in bypass mode by true bypassing it.

[R.G.]

The way the circuit works, the taper matters a whole lot more than the exact value. The pot is used as a voltage divider, and as long as its value is high enough not to load down Q1 and low enough not to be loaded down by Q2's input, the exact value is purely secondary. I would expect changes between 80K and 250K not to matter much.

[Paul Marossy]

The way the circuit works, the taper matters a whole lot more than the exact value. The pot is used as a voltage divider, and as long as its value is high enough not to load down Q1 and low enough not to be loaded down by Q2's input, the exact value is purely secondary. I would expect changes between 80K and 250K not to matter much.

Cool, thanks for that info R.G.

In the Maestro Boomerang, one of my favorite wah pedals, they actually use a 50K pot. I don't know how much of a difference that makes, but it does have more range mechanically than a CryBaby, which I think partly explains its different sound. There's a few other minor differences that also come into play, too.

[R.G.]

Mechanical traverse of the whole pot resistance range will be a big deal - as you know.

Beyond that, the pot value is significant only in that it's secondary loading affects the gain of Q1 or losses into Q2. One really interesting test is to put an emitter follower on the collector of Q1 to eliminate any pot loading on Q1. That lets you use pots well down in the 10K region without any loading. Changing Q2 to a darlington to run its input impedance up will let you use much higher values, although over 1M parasitic capacitance start eating some treble out of the signal which gets into Q2.

I've done both of these and they work fine - as does replacing Q1 and Q2 with opamps which do the same circuit function. Replacing Q1 with an opamp may be too "perfect" for some ears. An opamp there will not display the distortion of Q1 (which is what a lot of the dinking with resistor values changes) but will let you tailor the gain of "Q1" easily and therefore mess with the range of the wah. but replacing Q1 with an opamp will make any loading on the output essentially irrelevant.

Notice that an opamp version of the wah circuit does not cure input loading (tone sucking) issues, because Q1 has to be replaced with an opamp being an inverting amplifier. You'd still need to buffer the input to eliminate that. And for people who like the sound of loaded inputs, buffering in any form messes with what their ears like.

[liddokun]

Mechanical traverse of the whole pot resistance range will be a big deal - as you know.

Beyond that, the pot value is significant only in that it's secondary loading affects the gain of Q1 or losses into Q2. One really interesting test is to put an emitter follower on the collector of Q1 to eliminate any pot loading on Q1. That lets you use pots well down in the 10K region without any loading. Changing Q2 to a darlington to run its input impedance up will let you use much higher values, although over 1M parasitic capacitance start eating some treble out of the signal which gets into Q2.

I've done both of these and they work fine - as does replacing Q1 and Q2 with opamps which do the same circuit function. Replacing Q1 with an opamp may be too "perfect" for some ears. An opamp there will not display the distortion of Q1 (which is what a lot of the dinking with resistor values changes) but will let you tailor the gain of "Q1" easily and therefore mess with the range of the wah. but replacing Q1 with an opamp will make any loading on the output essentially irrelevant.

Notice that an opamp version of the wah circuit does not cure input loading (tone sucking) issues, because Q1 has to be replaced with an opamp being an inverting amplifier. You'd still need to buffer the input to eliminate that. And for people who like the sound of loaded inputs, buffering in any form messes with what their ears like.

Very enlightening post, R.G.
thanks

[aziltz]

anyone know what to use for a volume/expression pedal built into a wah enclosure?  Are there 100k Audio Wah Pots?

[R.G.]

anyone know what to use for a volume/expression pedal built into a wah enclosure?  Are there 100k Audio Wah Pots?

The Secret Life Of Pots", http://www.geofex.com, 8-31-99 (17 days less than ten years ago).